Various silicone rubber compositions of the so-called room temperature-curable type are known which cure at room temperature into rubber-like elastomers. Since the elastomers obtained from such compositions have excellent weatherability, durability, heat resistance, and low temperature resistance, the room temperature-curable silicone rubber compositions are used in various fields, and especially in the field of building construction, they are acquiring importance as a gap-filling sealant for joints in outside walls of buildings.
However, conventional silicone sealants have a problem that after the sealants are applied to joints, polyorganosiloxanes contained as a major component in the sealants penetrate into the areas surrounding the joints and dust particles in the air adhere to the surrounding areas to foul the areas.
For the purpose of overcoming the above problem, a silicone sealant containing a surfactant having a polyoxyethylene group, a sorbitan residue, a disaccharide residue, or the like (JP-A-56-76452 and JP-A-56-76453) and a silicone sealant containing a surfactant having a fluorine atom (JP-A-58-167647 and JP-A-61-34062) have been proposed. (The term "JP-" as used herein means an "unexamined published Japanese patent application".) However, these silicone sealants are defective in that the antifouling effect thereof does not last for a sufficiently long period of time.
On the other hand, a room temperature-curable composition containing as an effective ingredient a polyether the main chain of which consists essentially of a polyether terminated by a hydrolyzable silyl group has also been conventionally used as a building sealant. (The above polyether is disclosed in, for example, JP-A-50-156599 and the above composition is disclosed in, for example, JP-A-52-73998.) Although this kind of sealants causes no fouling of joint-surrounding areas unlike the above-described silicone sealants, they are poor in weatherability so that they lose their function as a sealant in a relatively short period of time with impaired rubber elasticity and cracking.
For the purpose of overcoming the above problems, the present inventor previously found that a composition comprising a silanol-terminated polydiorganosiloxane, a polymer obtained by the reaction of an epoxy-terminated polyether with a heterocyclic compound having two imino groups per molecule and/or an aromatic or heterocyclic compound having two mercapto groups and also an organosilicon compound having an epoxy group and a hydrolyzable group, an inorganic filler, and a curing catalyst shows excellent antifouling properties for a long period of time and also has excellent weatherability (Japanese Patent Application No. 63-289240 filed on Nov. 16, 1989). However, this composition is disadvantageous in that the surface of cured elastomer obtained from the composition remains tacky to show slightly poor antifouling properties in the case where the composition is modified to produce a composition which gives a cured elastomer having high elongation, such composition being particularly useful as a building sealant, or where the composition is cured in a high temperature and high humidity atmosphere.